This application claims the benefit of Korean Patent Application No. 2002-56191, filed Sep. 16, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a battery charging system and a charging method thereof, which can not only reduce the time of charging two or more batteries but also efficiently use an electrical power of a power source when two or more batteries are charged, and more particularly, to a battery charging system and a charging method of charging two or more batteries using an idle power.
2. Description of the Related Art
A portable computer, such as a notebook PC (personal computer), a PDA (personal digital assistant), a handheld PC, etc., is occasionally driven by a battery in a case where an adapter cannot be used for supplying electrical power. In this case, it is possible that two or more batteries are prepared for driving the portable computer for a long time.
Generally, the portable computer employs a rechargeable battery, such as a Li-ion battery, a polymer battery, etc. When the Li-ion or polymer battery is charged, a constant-current is continuously supplied to the battery in an early charging stage, which is called a constant-current charging mode. When the constant current is continuously supplied, an output voltage of the battery increases. Thereafter, when the output voltage of the battery reaches a predetermined voltage, an internal or external charging control part controls a voltage supplied to the battery not to increase higher than the predetermined voltage so as to prevent the battery from being overcharged. Hence, the battery is continuously charged at a constant voltage, which is called a constant-voltage charging mode.
A conventional charging method of charging the battery is as follows. FIG. 4 is a flowchart of the conventional charging method of charging two batteries, and FIG. 5 is a graph illustrating voltage and current variations when the two batteries are charged
As shown in FIGS. 4 and 5, in a case where first and second batteries are both charged, it is first sensed whether the electrical power for charging the first and second batteries is supplied from an adapter in operation P10. When the electrical power for charging the batteries is supplied from the adapter, the first battery starts to be charged in operation P12. At this time, an electrical current (i1) and an electrical voltage (v1) supplied to the first battery are illustrated in FIG. 5. When the first battery starts to be charged, the first battery is charged with a constant current (i1) (see an interval between t0 and t1). Herein, an interval (t0xcx9ct1) in which the current (i1) is kept constant is called a constant-current charging mode. In the constant-current charging mode, an output voltage of the first battery is gradually increased. When the output voltage of the battery reaches a predetermined voltage, an internal or external charging control part controls the voltage (v1) supplied to the first battery not to increase higher than the predetermined voltage so as to prevent the battery from being overcharged (see an interval between t1 and t2). Herein, an interval (t1xcx9ct2) in which the voltage (v1) is kept constant is called a constant-voltage charging mode. In the constant-voltage charging mode, the first battery is almost charged, and the current (i1) supplied to the first battery is gradually decreased.
Then, the charging control part (not shown) controlling the battery charging determines whether the first battery is charged completely in operation P14. Herein, completion of the battery charging is determined by depending on how much time is taken to charge a battery. When it is determined that the first battery is completely charged, the second battery starts to be charged in operation P16. Similarly, the second battery is charged through the constant-current charging mode (t2xcx9ct3) and the constant-voltage charging mode (t3xcx9ct4). When the second battery is completely charged, charging both of the first and second batteries is completed in operation P18.
As described above, when two or more batteries are charged according to the conventional battery charging method, one is completely charged and then the other one starts to be charged. That is, two or more batteries are charged one by one, so that it takes a relatively long time to charge the two or more batteries.
Further, in the constant-voltage charging mode (t1xcx9ct2 or t3xcx9ct4), the current (i1 or i2) supplied to the battery is gradually decreased, so that there is created an idle current being not supplied to the battery as much as the current (i1 or i2) is decreased.
Accordingly, it is an aspect of the present invention to provide a battery charging system and a charging method thereof, which can not only reduce a charging time of two or more batteries but also efficiently use an electrical power of a power source when two or more batteries are charged.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious form the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention are achieved by providing a battery charging system including two or more rechargeable batteries, a charging power supply charging the batteries with an external electric power, a charging power sensing part sensing at least one of a voltage and a current of a charging power supplied from the charging power supply to one of the batteries, and a charging control part controlling the charging power supply to supply another battery with an idle power created during charging the one battery according to a sensed result of the charging power sensing part.
According to an aspect of the invention, the charging control part determines that the idle power is created when the voltage supplied to the one battery is kept constant according to the sensed result of the charging power sensing part, and then controls the charging power supply to supply the idle power to the another battery.
According to an aspect of the invention, the charging control part determines that the idle power is created when the current supplied to the one battery is gradually decreased according to the sensed result of the charging power sensing part, and then controls the charging power supply to supply the idle power to the another battery.
According to another aspect of the present invention, the foregoing and/or other aspects may be also achieved by providing a battery charging method of charging two or more rechargeable batteries using a charging power supply charging the batteries with an external electric power. The method includes charging one of the batteries when the external electric power is supplied, sensing at least one of a voltage and a current of a charging power supplied to the one battery being charged, determining whether an idle power is created during charging the one battery according to a sensed result of the charging power, and controlling the charging power supply to supply the idle power to another battery when it is determined that the idle power is created.